REPORT OF MR. NELSON L. DERBY.
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asunder, and the whole mass of brick-work fell, carrying stairs and passages-with it, from the fourth story to the cellar,
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Austrian arched passage.
while fourteen workmen were killed. However, there are but few houses in the newer part of the city where these passages do not occur, and ordinary care proves sufficient to prevent such disasters.
Vaulting of masonry alone was formerly common in Austria in all stories of buildings, but is now confined, in most cases, to .the cellars, having been supplanted elsewhere by the extended use of iron. The ordinary cylindrical vault is employed occasionally, but the tendency seems to be to transfer the weight of the superstructure to special points or pillars, rather than to continuous walls, after the principles of the Gothic architecture. In this way the same stability is secured, with a less expenditure of material; and German writers contend that the necessities of building are thus met in the most rational manner. A passage, for instance, is to be built and covered by masonry alone. Instead of erecting two walls of uniform thickness, and joining them above by a cylindrical vault, a row of pillars is built, having, in special cases, the width of the passage for their distance apart in the row. Each pillar is then connected by a strong arch of several superposed layers of brick with the one opposite it, and the °ue on each side of it. In this way the length of the passage 18 divided into squares, and each of these is covered by a light vault of spherical form, supported by four of the arches described. The spaces left between the pillars in row, are
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